There are conventional furcation tubes for protecting standard sized tight-buffered optical fibers having an outer diameter of 900 microns (0.900 mm). These conventional furcation tubes are also suitable for protecting bare optical fibers, i.e., optical fibers having an outer diameter of 250 microns (0.250 mm). However, the outside diameter of the conventional furcation tubes are so relatively large that they become impractical to be used in, for instance, premise networks, where space is at a premium. In other words, the available space cannot accommodate the desired number of furcation tubes. If the outside diameter of the conventional furcation tubes were to be reduced to accommodate the space requirements and still allow tight-buffered optical fibers to fit therethrough, the walls of the protective casing become too weak, thereby allowing the protective casings to kink when bent into the required radii or wound on a reel. This kinking of the furcation tube can induce induce high stress levels, which can cause undesirable damage to the optical fibers and/or reducing of, or eliminating, of the light transmission along the optical fibers.
FIG. 1 depicts one such conventional furcation tubing 10 that is currently used for standard sized tight-buffered optical fibers having an outer diameter of 900 microns (0.9 mm). Furcation tubing 10 has an outer tubing 12, which is typically a PVC jacket and has a relatively large outer diameter of about 2900 microns (2.9 mm). A layer of aramid yarns 14 acting as flexible strength members are disposed between outer tubing 12 and an inner tubing 16. Inner tubing 16 has a central passageway 18 that is about 1070 microns (1.07 mm) in diameter for allowing the standard sized tight-buffered optical fiber to pass therethrough. The inner tubing 16 is typically made from PDVF (Polyvinylidene fluoride) or TFE (tetrafluoroethylene). To prevent the protective casing 10 from collapsing during use, the inner tubing 16 requires a relatively thick wall thickness of about 400 microns (0.4 mm). However, this required wall thickness for inner tubing 16 causes the relatively large overall size of the protective casing, i.e., 2900 microns (2.9 mm) and limits the number of furcation tubes that can pass through a given space.
Other conventional furcation tubes having smaller outer diameters are known, but in order to prevent kinking the furcation tubes and/or undesired optical attenuation require inner diameters that are too small for accommodating the standard sized tight-buffered optical. Generally speaking, these smaller conventional furcation tubes include an inner tubing having a relatively thick wall thickness to inhibit kinking and/or undesirable optical attenuation. By way of example, U.S. Pat. No. 5,201,020 discloses a protective tubing having an outside diameter of 900 microns and an inner diameter of about 500 microns. Consequently, the protective tubing is suitable for bare optical fibers, but is not suitable for receiving tight-buffered optical fibers having an outer diameter of 900 microns.
Accordingly, the present invention is directed to a protective casing that substantially obviates one or more of the problems and disadvantages in the prior art. Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the apparatus and process particularly pointed out in the written description and claims, as well as the appended drawings.